<!DOCTYPE html>
<html lang="zh-cn">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>事件流</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        #out_box {
            width: 450px;
            height: 450px;
            background-color: #987654;
            text-align: center;
            position: relative;
            top: 100px;
            left: 100px;
        }
        
        #inner_box {
            width: 300px;
            height: 300px;
            background-color: #4365c3;
            line-height: 300px;
            position: absolute;
            top: 75px;
            left: 75px;
        }
    </style>
</head>

<body>
    <div id="out_box">
        <div id="inner_box">课工场</div>
    </div>
</body>

</html>
<script>
    let inner = window.document.querySelector('#inner_box');
    inner.addEventListener('click', function(param) {
        window.alert("inner_box");
    });
    let out = window.document.querySelector('#out_box');
    out.addEventListener('click', function(param) {
        window.alert("out_box");
    });
</script>